EP0226071A2 - Low temperature sintered ceramic capacitor with a temperature compensating capability, and method of manufacture - Google Patents
Low temperature sintered ceramic capacitor with a temperature compensating capability, and method of manufacture Download PDFInfo
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- EP0226071A2 EP0226071A2 EP86116195A EP86116195A EP0226071A2 EP 0226071 A2 EP0226071 A2 EP 0226071A2 EP 86116195 A EP86116195 A EP 86116195A EP 86116195 A EP86116195 A EP 86116195A EP 0226071 A2 EP0226071 A2 EP 0226071A2
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- oxide
- silicon dioxide
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- 238000000034 method Methods 0.000 title claims description 13
- 239000003985 ceramic capacitor Substances 0.000 title description 12
- 239000000203 mixture Substances 0.000 claims abstract description 73
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims abstract description 53
- 239000003990 capacitor Substances 0.000 claims abstract description 51
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- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 description 1
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Images
Classifications
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
- H01G4/00—Fixed capacitors; Processes of their manufacture
- H01G4/30—Stacked capacitors
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
- C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
- C04B35/48—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on zirconium or hafnium oxides, zirconates, zircon or hafnates
- C04B35/49—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on zirconium or hafnium oxides, zirconates, zircon or hafnates containing also titanium oxides or titanates
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
- C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
- C04B35/46—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on titanium oxides or titanates
- C04B35/462—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on titanium oxides or titanates based on titanates
- C04B35/465—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on titanium oxides or titanates based on titanates based on alkaline earth metal titanates
- C04B35/47—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on titanium oxides or titanates based on titanates based on alkaline earth metal titanates based on strontium titanates
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
- H01G4/00—Fixed capacitors; Processes of their manufacture
- H01G4/002—Details
- H01G4/018—Dielectrics
- H01G4/06—Solid dielectrics
- H01G4/08—Inorganic dielectrics
- H01G4/12—Ceramic dielectrics
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
- H01G4/00—Fixed capacitors; Processes of their manufacture
- H01G4/002—Details
- H01G4/018—Dielectrics
- H01G4/06—Solid dielectrics
- H01G4/08—Inorganic dielectrics
- H01G4/12—Ceramic dielectrics
- H01G4/1209—Ceramic dielectrics characterised by the ceramic dielectric material
- H01G4/1236—Ceramic dielectrics characterised by the ceramic dielectric material based on zirconium oxides or zirconates
- H01G4/1245—Ceramic dielectrics characterised by the ceramic dielectric material based on zirconium oxides or zirconates containing also titanates
Definitions
- Our invention relates to solid dielectric capacitors, and more specifically to ceramic capacitors such as those of the monolithic, multilayered configuration that are capable of manufacture by cosintering at sufficinetly low temperatures to permit the use of base metal electrodes, and to a process for the fabrication of such low temperature sintered capacitors.
- the ceramic capacitors of our invention are particularly notable for their temperature compensating capability, having a practically constant temperature coefficient of capacitance in the normal range of temperatures in which they are intended for use.
- Multilayered ceramic capacitors have been known which employ noble metals such as platinum and palladium as the electrode materials.
- noble metals such as platinum and palladium
- An electroconductive paste containing powdered platinum or palladium is then "printed” on the green sheets in a desired pattern.
- a plurality of such printed green sheets are stacked up, pressed together, and sintered in a temperature range of 1300 * to 1600 . C. in an oxidative atmosphere.
- Japanese Laid Open Patent Application No. 53-98099 suggests a solution to the above discussed problem, particularly in regard to the manufacture of temperature compensating ceramic capacitors.
- This patent application teaches ceramic compositions comprising calcium zirconate (CaZrO 3 ) and manganese dioxide (Mn0 2 ).
- CaZrO 3 calcium zirconate
- Mn0 2 manganese dioxide
- the dielectric bodies of these known compositions are sinterable in a reductive atmosphere, so that electrodes of nickel or like base metal can be employed for cosintering with the dielectric bodies without the danger of oxidation.
- our invention provides a low temperature sintered solid dielectric capacitor comprising a dielectric ceramic body and at least two electrodes in contact therewith.
- the dielectric ceramic body consists essentially of 100 parts by weight of (CaO) k ⁇ (Zr 1-x Ti x )O 2 , where k is a numeral in the range of 0.8 to 1.3 inclusive, and x a numeral in the range of zero to 0.3 inclusive, and 0.2 to 10.0 parts by weight of an additive mixture of boric oxide (B 0 ), silicon dioxide (Si0 2 ), and at least one metal oxide selected from the group consisting of barium oxide (BaO), magnesium oxide (Mg0), zinc oxide (Zn0), strontium oxide (Sr0) and calcium oxide (CaO).
- BaO boric oxide
- Si0 2 silicon dioxide
- CaO calcium oxide
- the relative proportions of B 2 O 3 , SiO 2 and at least one selected metal oxide, altogether constituting the additive mixture will be specifically determined in connection with a tern
- the subscript x in the above defined formula of the major ingredient may be zero in accordance with our invention.
- the major ingredient may also be expressed as (Cao) k ⁇ (Me)O 2 , where Me is either Zr or (Zr + Ti).
- the ceramic capacitor of our invention has proved to be very well suited for temperature compensating applications in oscillator and other circuits.
- the test capacitors manufactured in accordance with our invention had specific dielectric constants of over 30 at one megahertz (MHz), temperature coefficients of capacitances of +30 to -700 ppm per degree C., Q factors of over 2000 at 1 MHz, and resistivities of 1 x 10 megohm-centimeters or more.
- the Q factor rises to as much as 5000 or more if the dielectric body contains from 0.2 to 5.0 parts by weight of the additive mixture with respect to 100 parts of the major ingredient.
- Another aspect of our invention is a method of fabricating the above defined ceramic capacitor.
- the method dictates, first of all, the preparation of of a mixture of the above indicated proportions of the major ingredient and additives in finely divided form. This mixture is then molded into a body of desired shape and size, which is provided with at least two electrode portions of an electroconductive material in any convenient manner. Then the molding with the electrode portions is sintered in a nonoxidative (i.e. reductive or neutral) atmosphere and is subsequently reheated in an oxidative atmosphere.
- a nonoxidative i.e. reductive or neutral
- FIG. 1 We have illustrated in FIG. 1 one of many like monolithic ceramic capacitors fabricated in the subsequent Examples of our invention by way of a preferable embodiment thereof.
- the representative capacitor is shown to have an interlamination of three dielectric ceramic layers 12 and two film electrodes 14.
- the three ceramic layers 12 constitute in combination a solid dielectric body 15 having the low temperature sintered ceramic compositions in accordance with our invention.
- a pair of conductive terminations 16 contact the respective film electrodes 14.
- Each termination 16 is shown to comprise a baked on zinc layer 18, a plated on copper layer 20, and a plated on solder layer 22.
- the intermediate one of the three dielectric layers 12 has a thickness of 0.02 millimeter.
- the area of that part of each film electrode 14 which overlaps the other film electrode is 25 square millimeters (5 x 5 millimeters).
- test capacitors each constructed as in FIG. 1, some having their dielectric bodies formulated in accordance with the ceramic compositions of our invention and others not, and measured their electrical properties. Table 1 lists the compositions of the dielectric bodies of all the test capacitors fabricated.
- the major ingredient of the ceramic compositions in accordance with our invention has been herein defined as (CaO) k ⁇ (Zr 1-x Ti x )O 2 , or (Ca0) k ⁇ (Me)0 2 , where Me is either Zr or (Zr + Ti). Accordingly, in Table 1, we have given various combinations of the atomic numbers k and x in the formula to indicate the specific major ingredients employed in the various Tests.
- the ceramic compositions of our invention further include mixtures, in various proportions, of additives B 2 O 3 , SiO 2 and MO.
- Table 1 specifies the amounts, in parts by weight, of the additive mixtures with respect to 100 parts by weight of the major ingredient, as well as the relative proportions, in mole percent, of the additives B 2 O 3 , SiO 2 and MO. Further, since MO can be any one or more or BaO, MgO, ZnO, Sr0 and CaO, Table 1 gives the relative proportions, in mole percent, of these metal oxides, wherever one or more of them are employed.
- the major ingredient of the dielectric bodies of the capacitors of Test No. 1 was CaO.(Zr 0.98 Ti 0.02 )O 2 .
- One hundred parts of this major ingredient was admixed with 3.0 parts by weight of a mixture of 15 mole percent B 2 O 3 , 25 mole percent SiO and 60 mole percent M0.
- MO was a mixture of 60 mole percent Sr0 and 40 mole percent CaO.
- the other additives BaO, Mg0 and Zn0 were not used in this particular Test.
- start materials had all purities of not less than 99.0 percent.
- the above specified weights of the start materials do not include those of the impurities contained.
- this additive mixture Thirty grams (three weight percent) of this additive mixture was added to 1000 grams of the above prepared major ingredient. Further, to this mixture, we added 15 percent by weight of an organic binder and 50 percent by weight of water with respect to the total weight of the major ingredient and additives.
- the organic binder was an aqueous solution of acrylic ester polymer, glycerine, and condensed phosphate. The mixture of all these was ball milled into a slurry. Then this slurry was defoamed in vacuum.
- the defoamed slurry was charged into a reverse roll coater thereby to be shaped into a thin, continuous strip on an elongate supporting strip of polyester film. Then the strip was dried by heating to 100° C. on the supporting film.
- the green ceramic strip thus obtained, approximately 25 microns thick, was subsequently punched into "squares" sized 10 by 10 centimeters. These green ceramic squares are to become the ceramic layers 12, FIG. 1, in the completed test capacitors 10.
- two green squares were stacked, with their printings directed upwardly, and with the printings on the two squares offset from each other to an extent approximately half the pitch of their patterns in the longitudinal direction.
- the thus stacked two printed squares were placed between two separate stacks of four unprinted squres each with a thickness of 60 microns.
- the resulting stack of printed and unprinted squares were pressed in their thickness direction under a pressure of approximately 40 tons at 50 . C, thereby firmly bonding the stacked squares to one another. Then the bonded squares were cut in a latticed pattern into 50 laminate chips of identical construction.
- Tests Nos. 2 through 67 we made similar capacitors through exactly the same procedure as that set forth in the foregoing in connection the Test No. 1 composition, except for the temperature of sintering in the reductive atmosphere, which will be referred to presently.
- each test capacitor was first measured at a temperature of 20° C., a frequency of one megahertz, and an effective alternating current voltage of 0.5 volt. Then the specific dielectric constant was computed from the measured value of capacitance, the area (25 square millimeters) of each of the overlapping parts of the two film electrodes 14, and the thickness (0.05 millimeter) of that ceramic layer 12 which intervenes between the film electrodes.
- the Q factor was measured by a Q meter at a frequency of one megahertz, a temperature of 20° C., and an effective alternating current voltage of 0.5' volt.
- Resistance between the pair of conductive terminations 16 of each test capacitor was measured after the application of a direct current voltage of 50 volts for one minute at a temperature of 20° C. Then the resistivity was computed from the measured resistance value and the size of the test capacitors.
- Table 2 gives the results of the measurements by the above described methods, as well as the maximum temperatures at which the test capacitors were sintered in the reductive atmosphere during their manufacture. It will be noted from this table that the specific dielectric constants of the Test No. 1 capacitors, for instance, averaged 33, their temperature coefficients -10 ppm per degree C., their Q factors 8200, and their resistivities 2.6 x 10 megohm-centimeters. The temperature coefficients of the capacitances of the test capacitors were practically constant in the normal range of their operating temperatures, making the capacitors well suited for use as temperature compensating capacitors.
- the ceramic compositions of Tests Nos. 39, 46 and 51 contained no additive specified by our invention.
- the dielectric bodies formulated accordingly were not coherently bonded on firing at a temperature as high as 1300 * C.
- the ceramic compositions of Tests Nos. 40, 47 and 52 for comparison. They contained 0.2 part by weight of the additives with respect to 100 parts by weight of the major ingredient. Even though the firing temperature was as low as 1160-1180 . C., the resulting test capacitors possess the desired electrical characteristics.
- We set, therefore, the lower limit of the possible proportions of the additive mixture at 0.2 part by weight with respect to 100 parts by weight of the major ingredient.
- the Tests Nos. 45, 50 and 55 ceramic compositions contained as much as 12 parts by weight of the additives with respect to 100 parts by weight of the major ingredient.
- the resulting Tests Nos. 45, 50 and 55 capacitors have average Q factors of 1050, 1050 and 1130, respectively, which are all far less than the above established criterion of 3200.
- the proportion of the additive mixture was reduced to 10 parts by weight, as in Tests Nos. 44, 49 and 54, the resulting capacitors have all the desired characteristics. Therefore, the upper limit of the possible proportions of the additive mixture is set at 10 parts by weight with respect to 100 parts by weight of the major ingredient.
- (CaO) k ⁇ (Zr 1-x Ti x )O 2 the value of x was set at 0.35 and more in Tests Nos. 37 and 38. In the resulting capacitors the temperature coefficient of capacitance is -840 and -980, both outside the desired range of -690 to +30. When the value of x was decreased to not more than 0.30, as in Test No. 36, then the desired electrical charactristics were all obtained. The highest possible value of x is therefore 0.30. Test No. 28 indicates that the desired electrical characteristics are obtainable if the value of x is zero, that is, if the major ingredient does not include titanium. The Q factor becomes-relatively high if the value of x is reduced to less than 0.20.
- the value of k in the formula of the major ingredient was set at 0.7 in Tests Nos. 56 and 62.
- the resistivities of the resulting capacitors were 5.4 x 10 and 3.6 x 10 3 , both much lower than the desired lower limit of 1 x 10 7 .
- the desired value of resistivity was obtained when the value of k was increased to 0.8 as in Test No. 57 and 63.
- the lowermost possible value of k is therefore 0.8.
- the value of k was made as much as 1.4 as in Tests Nos. 61 and 67, the resulting dielectric bodies were not coherently bonded on firing at as high a temperature as 1300° C.
- the desired electrical characteristics were obtained when the value of k was reduced to 1.3 as in Tests Nos. 60 and 66. Accordingly, the greatest possible value of k is 1.3.
- the point A in the ternary diagram indicates the Test No. 1 additive composition of 15 mole percent B 2 O 3 , 25 mole percent SiO 2 and 60 mole percent MO.
- the point B indicates the Test No. 2 additive composition of 30 mole percent B 0 , zero mole percent Si0 and 70 mole percent MO.
- the point C indicates the Test No. 3 additive com p osi- tion of 90 mole percent B 0 , zero mole percent SiO 2 and 10 mole percent MO.
- the point D indicates the Test No. 4 additive composition of 90 mole percent B 2 O 3 , 10 mole percent SiO 2 and zero mole percent MO.
- the point E indicates the Test No. 5 additive composition of 25 mole percent B 0 , 75 mole percent SiO 2 and zero mole percent MO.
- the relative proportions of the additives B 0 , SiO 2 and MO of the ceramic compositions in accordance with our invention are within the region bounded by the lines sequentially connecting the above stated points A, B, C, D and E in the ternary diagram of FIG. 2.
- Tables 1 and 2 prove that the additive compositions within the above defined region makes possible the provision of capacitors of the desired electrical characteristics.
- the additive compositions of Tests Nos. 23-27 all fall outside that region, and the corresponding dielectric bodies were not coherently bonded on firing at a temperature of 1250 * C.
- the above specified acceptable range of the relative proportions of the additives holds true regardless of whether only one of BaO, MgO, ZnO, Sr0 and CaO is employed as MO, as in Tests Nos. 9-13, or two or more or all of them are employed in suitable relative proportions as in other Tests.
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Abstract
Description
- Our invention relates to solid dielectric capacitors, and more specifically to ceramic capacitors such as those of the monolithic, multilayered configuration that are capable of manufacture by cosintering at sufficinetly low temperatures to permit the use of base metal electrodes, and to a process for the fabrication of such low temperature sintered capacitors. The ceramic capacitors of our invention are particularly notable for their temperature compensating capability, having a practically constant temperature coefficient of capacitance in the normal range of temperatures in which they are intended for use.
- Multilayered ceramic capacitors have been known which employ noble metals such as platinum and palladium as the electrode materials. Generally, for the manufacture of such multilayered capacitors, there are first prepared "green" (unsintered) dielectric sheets from the proportioned ingredients of a desired dielectric ceramic material in finely divided form. An electroconductive paste containing powdered platinum or palladium is then "printed" on the green sheets in a desired pattern. A plurality of such printed green sheets are stacked up, pressed together, and sintered in a temperature range of 1300* to 1600. C. in an oxidative atmosphere.
- This conventional method makes possible the simultaneous production (cosintering) of the dielectric ceramic layers and the film electrodes interleaved therewith. It is also an acknowledged advantage of the known method that the nobel metal electrodes are totally unaffected by the high temperature sintering in an oxidative atmosphere. Offsetting all these advantages is the expensiveness of the noble metals, which add considerably to the costs of the multilayered ceramic capacitors.
- Japanese Laid Open Patent Application No. 53-98099 suggests a solution to the above discussed problem, particularly in regard to the manufacture of temperature compensating ceramic capacitors. This patent application teaches ceramic compositions comprising calcium zirconate (CaZrO3) and manganese dioxide (Mn02). In the manufacture of ceramic capacitors the dielectric bodies of these known compositions are sinterable in a reductive atmosphere, so that electrodes of nickel or like base metal can be employed for cosintering with the dielectric bodies without the danger of oxidation.
- We do, however, object to the prior art CaZrO - MnO 2 ceramic compositions for several reasons. These known ceramic compositions require firing in as high a temperature range as from 1350* to 1380* C. When the green sheets of the ceramic compositions, having a paste composed primarily of powdered nickel printed thereon, are sintered in that temperature range, the nickel particles tend to grow and flocculate in spite of the nonoxidative atmosphere in which they are fired. We have also found that the base metal particles are easy to diffuse into the ceramic bodies when fired in that temperature range. The flocculation and diffusion of the base metal particles are, of course, both undesirable as the resulting capacitors may fail to possess desired values of capacitance and insulation resistance.
- We have hereby discovered how to reduce the firing temperature of ceramic bodies, particularly in the manufacture of temperature compensating capacitors by the cosintering of ceramic bodies and electrodes, to make possible the use of a low cost base metal as the electrode material without the noted difficulties encountered heretofore.
- Stated briefly in one aspect thereof, our invention provides a low temperature sintered solid dielectric capacitor comprising a dielectric ceramic body and at least two electrodes in contact therewith. The dielectric ceramic body consists essentially of 100 parts by weight of (CaO)k·(Zr1-xTix)O2, where k is a numeral in the range of 0.8 to 1.3 inclusive, and x a numeral in the range of zero to 0.3 inclusive, and 0.2 to 10.0 parts by weight of an additive mixture of boric oxide (B 0 ), silicon dioxide (Si02), and at least one metal oxide selected from the group consisting of barium oxide (BaO), magnesium oxide (Mg0), zinc oxide (Zn0), strontium oxide (Sr0) and calcium oxide (CaO). The relative proportions of B2O3, SiO2 and at least one selected metal oxide, altogether constituting the additive mixture, will be specifically determined in connection with a ternary diagram attached hereto.
- The subscript x in the above defined formula of the major ingredient may be zero in accordance with our invention. Thus the major ingredient may also be expressed as (Cao)k·(Me)O2, where Me is either Zr or (Zr + Ti).
- The ceramic capacitor of our invention,'having its dielectric body formulated as set forth in the foregoing, has proved to be very well suited for temperature compensating applications in oscillator and other circuits. The test capacitors manufactured in accordance with our invention had specific dielectric constants of over 30 at one megahertz (MHz), temperature coefficients of capacitances of +30 to -700 ppm per degree C., Q factors of over 2000 at 1 MHz, and resistivities of 1 x 10 megohm-centimeters or more. The Q factor rises to as much as 5000 or more if the dielectric body contains from 0.2 to 5.0 parts by weight of the additive mixture with respect to 100 parts of the major ingredient.
- Another aspect of our invention is a method of fabricating the above defined ceramic capacitor. The method dictates, first of all, the preparation of of a mixture of the above indicated proportions of the major ingredient and additives in finely divided form. This mixture is then molded into a body of desired shape and size, which is provided with at least two electrode portions of an electroconductive material in any convenient manner. Then the molding with the electrode portions is sintered in a nonoxidative (i.e. reductive or neutral) atmosphere and is subsequently reheated in an oxidative atmosphere.
- We recommend a temperature range of 1000* to 1200* C. for sintering the dielectric molding. This temperature range is sufficiently low to permit the cosintering, in a reductive or neutral atmosphere, of nickel or like base metal electrodes on the dielectric molding without the likelihood of the flocculation or diffusion of the base metal.
- The above and other features and advantages of our invention and the manner of realizing them will become more apparent, and the invention itself will best be understood, from a study of the following description and appended claims taken together with the attached drawings.
-
- FIG. 1 is a sectional representation of a monolithic, multilayered ceramic capacitor in accordance with our invention, the illustrated capacitor being representative of numerous test capacitors fabricated in the Examples of our invention to be presented subsequently; and
- FIG. 2 is a ternary diagram depicting the relative proportions of the additives of the ceramic compositions in accordance with our invention.
- We have illustrated in FIG. 1 one of many like monolithic ceramic capacitors fabricated in the subsequent Examples of our invention by way of a preferable embodiment thereof. Generally designated 10, the representative capacitor is shown to have an interlamination of three dielectric ceramic layers 12 and two
film electrodes 14. The three ceramic layers 12 constitute in combination a soliddielectric body 15 having the low temperature sintered ceramic compositions in accordance with our invention. The twofilm electrodes 14, which can be of a low cost base metal such as nickel, extend from the opposite sides of thedielectric body 15 toward, and terminate short of, the other sides of the dielectric body and so have an overlapping, parallel spaced relation to each other. A pair ofconductive terminations 16 contact therespective film electrodes 14. Eachtermination 16 is shown to comprise a baked onzinc layer 18, a plated oncopper layer 20, and a plated onsolder layer 22. - Typically, and as fabricated in the subsequent Examples of our invention, the intermediate one of the three dielectric layers 12 has a thickness of 0.02 millimeter. The area of that part of each
film electrode 14 which overlaps the other film electrode is 25 square millimeters (5 x 5 millimeters). - We fabricated 67 different sets of test capacitors, each constructed as in FIG. 1, some having their dielectric bodies formulated in accordance with the ceramic compositions of our invention and others not, and measured their electrical properties. Table 1 lists the compositions of the dielectric bodies of all the test capacitors fabricated.
- The major ingredient of the ceramic compositions in accordance with our invention has been herein defined as (CaO)k·(Zr1-xTix)O2, or (Ca0)k·(Me)02, where Me is either Zr or (Zr + Ti). Accordingly, in Table 1, we have given various combinations of the atomic numbers k and x in the formula to indicate the specific major ingredients employed in the various Tests. The ceramic compositions of our invention further include mixtures, in various proportions, of additives B2O3, SiO2 and MO. Table 1 specifies the amounts, in parts by weight, of the additive mixtures with respect to 100 parts by weight of the major ingredient, as well as the relative proportions, in mole percent, of the additives B2O3, SiO2 and MO. Further, since MO can be any one or more or BaO, MgO, ZnO, Sr0 and CaO, Table 1 gives the relative proportions, in mole percent, of these metal oxides, wherever one or more of them are employed.
- According to Table 1, the major ingredient of the dielectric bodies of the capacitors of Test No. 1 was CaO.(Zr0.98Ti0.02)O2. One hundred parts of this major ingredient was admixed with 3.0 parts by weight of a mixture of 15 mole percent B2O3, 25 mole percent SiO and 60 mole percent M0. MO was a mixture of 60 mole percent Sr0 and 40 mole percent CaO. The other additives BaO, Mg0 and Zn0 were not used in this particular Test.
- For the fabrication of the capacitors of Test No. 1 we started with the preparation of the major ingredient of their dielectric bodies. We prepared the following start materials:
- Calcium carbonate (CaCO )
- 541.14 grams (1.00 mole part) Zirconium oxide (ZrO2)
- 650.23 grams (0.98 mole part) Titanium oxide (TiO2)
- 8.62 grams (0.02 mole part)
- These start materials had all purities of not less than 99.0 percent. The above specified weights of the start materials do not include those of the impurities contained. We charged the start materials into a pot mill together with alumina balls and 2.5 liters of water and mixed them together for 15 hours. Then the mixture was introduced into a stainless steel vat and therein dried by air heated to 150° C. for four hours. Then the dried mixture was crushed into relatively coarse particles, which were subsequently fired in air within a tunnel furnace at 1200° C. for two hours. There was thus obtained the major ingredient of the above specified composition in finely divided form.
-
- To these substances we added 300 cubic centimeters of alcohol, and the resulting slurry was stirred for 10 hours in a polyethylene pot with alumina balls. Then the mixture was air fired at 1000* C. for two hours. Then, charged into an alumina pot together with 300 cubic centimeters of water, the fired mixture was pulverized with alumina balls over a period of 15 hours. Then the pulverized mixture was dried at 150° C. for four hours. There was thus obtained in finely divided form the desired additive mixture of 15 mole percent B 0 , 25 mole percent SiO2 and 60 mole percent M0, with the MO consisting of 36 mole percent Sr0 and 24 mole percent CaO.
- Thirty grams (three weight percent) of this additive mixture was added to 1000 grams of the above prepared major ingredient. Further, to this mixture, we added 15 percent by weight of an organic binder and 50 percent by weight of water with respect to the total weight of the major ingredient and additives. The organic binder was an aqueous solution of acrylic ester polymer, glycerine, and condensed phosphate. The mixture of all these was ball milled into a slurry. Then this slurry was defoamed in vacuum.
- Then the defoamed slurry was charged into a reverse roll coater thereby to be shaped into a thin, continuous strip on an elongate supporting strip of polyester film. Then the strip was dried by heating to 100° C. on the supporting film. The green ceramic strip thus obtained, approximately 25 microns thick, was subsequently punched into "squares" sized 10 by 10 centimeters. These green ceramic squares are to become the ceramic layers 12, FIG. 1, in the completed
test capacitors 10. - For the fabrication of the base
metal film electrodes 14 on the ceramic layers 12, we prepared 10 grams of nickel in finely divided form, with an average particle size of 1.5 microns, and a solution of 0.9 gram of ethyl cellulose in 9.1 grams of butyl "Carbitol" (trademark for diethylene glycol monobutyl ether). Both were intimately interminged by being agitated for 10 hours, thereby providing an electroconductive paste. Then this paste was "printed" on one surface of each green ceramic square, which had been prepared as above described, through a screen having 50 perforations of rectangular shape, each sized seven by 14 millimeters. - After drying the printed paste, two green squares were stacked, with their printings directed upwardly, and with the printings on the two squares offset from each other to an extent approximately half the pitch of their patterns in the longitudinal direction. The thus stacked two printed squares were placed between two separate stacks of four unprinted squres each with a thickness of 60 microns. The resulting stack of printed and unprinted squares were pressed in their thickness direction under a pressure of approximately 40 tons at 50. C, thereby firmly bonding the stacked squares to one another. Then the bonded squares were cut in a latticed pattern into 50 laminate chips of identical construction.
- We employed a furnace capable of atmosphere control for cofiring the above prepared green dielectric bodies and, buried therein, the conductive layers which were to become the
film electrodes 14 in the completedcapacitors 10. The chips were first air heated in this furnace to 600` C. at a rate of 100* C. per hour, thereby driving off the organic binder that had been used for providing the slurry of the powdered major ingredient and additives. Then the furnace atmosphere was changed from air to a reductive (nonoxidative) atmosphere consisting of two percent by volume of molecular hydrogen and 98 percent by volume of molecular nitrogen. In this reductive atmosphere the furnace temperature was raised from 600° C. to 1120° C. at a rate of 100* C. per hour. The maximum temperature of 1120. C., at which the ceramic bodies formulated in accordance with our invention were to be sintered to maturity, was maintained for three hours. Then the furnace temperature was lowered to 600° C. at a rate of 100° C. per hour. Then, with the furnace atmosphere again changed to air (oxidative atmosphere), the temperature of 600* C. was maintained for 30 minutes for the oxidizing heat treatment of the sintered chips. Then the furnace temperature was allowed to drop to room temperature. - There were thus obtained the dielectric
ceramic bodies 15, FIG. 1, cosintered with thefilm electrodes 14 buried therein. - We proceeded to the production of the pair of
conductive terminations 16 on both sides of eachceramic body 15 through which are exposed thefilm electrodes 14. First, for the production of the inmost zinc layers 18, a conductive paste composed of zinc, glass frit and vehicle was coated on both sides of eachceramic body 15. The coatings on drying were air heated to 550 C. and maintained at that temperature for 15 minutes, thereby completing the zinc layers 18 each in direct contact with one of the twofilm electrodes 14. Then the intermediate copper layers 20 were formed over the zinc layers 18 by electroless plating. Then the outermost solder layers 22 were formed by electroplating a lead tin alloy over the copper layers 20. - We have thus completed the fabrication of monolithic, multilayered ceramic test capacitors, each constructed as in FIG. 1, in accordance with the ceramic composition of Test No. 1 of Table 1. The composition of the
ceramic bodies 15 of the thus completed capacitors proved substantially akin to that before sintering. It is therefore reasoned that the sinteredceramic bodies 15 are of perovskite structures, with the additives (15 mole percent B 0 , 25 mole percent SiO2, 36 mole percent Sr0 and 24 mole percent Ca0) uniformly dispersed among the crystal grains of the major ingredient. - As for the other ceramic compositions of Table 1, designated Tests Nos. 2 through 67, we made similar capacitors through exactly the same procedure as that set forth in the foregoing in connection the Test No. 1 composition, except for the temperature of sintering in the reductive atmosphere, which will be referred to presently.
- All the capacitors of Test Nos. 1 through 67 were then tested as to their specific dielectric constants, temperature coefficients, Q factors, and resistivities. The following are the methods we employed for the measurement of these properties:
- The capacitance of each test capacitor was first measured at a temperature of 20° C., a frequency of one megahertz, and an effective alternating current voltage of 0.5 volt. Then the specific dielectric constant was computed from the measured value of capacitance, the area (25 square millimeters) of each of the overlapping parts of the two
film electrodes 14, and the thickness (0.05 millimeter) of that ceramic layer 12 which intervenes between the film electrodes. -
- The Q factor was measured by a Q meter at a frequency of one megahertz, a temperature of 20° C., and an effective alternating current voltage of 0.5' volt.
- Resistance between the pair of
conductive terminations 16 of each test capacitor was measured after the application of a direct current voltage of 50 volts for one minute at a temperature of 20° C. Then the resistivity was computed from the measured resistance value and the size of the test capacitors. - Table 2 gives the results of the measurements by the above described methods, as well as the maximum temperatures at which the test capacitors were sintered in the reductive atmosphere during their manufacture. It will be noted from this table that the specific dielectric constants of the Test No. 1 capacitors, for instance, averaged 33, their temperature coefficients -10 ppm per degree C., their Q factors 8200, and their resistivities 2.6 x 10 megohm-centimeters. The temperature coefficients of the capacitances of the test capacitors were practically constant in the normal range of their operating temperatures, making the capacitors well suited for use as temperature compensating capacitors.
- It will be observed from Table 2 that the dielectric bodies of Tests Nos. 23-27, 39, 46, 51, 61 and 67 were not coherently bonded on firing at temperatures as high as 12500 or 13000 C. in the reductive atmosphere. The corresponding ceramic compositions of Table 1 fall outside the scope of our invention. The dielectric bodies of all the other Tests could be sintered to maturity at temperatures less than 1200° C.
- Before proceeding further with the examination of the results of Table 2 we will determine the acceptable criteria of the four electrical properties in question for the temperature compensating ceramic capacitors provided by our invention. These criteria are:
- Specific dielectric constant:
- From 30 to 67.
- Temperature coefficient of capacitance:
- From -690 to +30 ppm per degree C.
- Q factor:
- Not less than 3200.
- Resistivity: 7
- Not less than 1 x 10 megohm-centimeters.
- A reconsideration of Table 1 in light of the above established criteria of favorable electrical characteristics will reveal that the capacitors of Tests Nos. 37, 38, 45, 50, 55, 56 and 62 do not meet these criteria. Accordingly, the corresponding ceramic compositions of Table 1 also fall outside the scope of our invention. All the test capacitors but those of Tests Nos. 23-27, 37-39, 45, 46, 50, 51, 55, 56, 61, 62 and 67 satisfy the criteria, so that their ceramic compositions are in accord with our invention.
- Now, let us study the ceramic compositions of Table 1 and the corresponding capacitor characteristics, as well as the sintering temperatures, of Table 2 in more detail. The ceramic compositions of Tests Nos. 39, 46 and 51 contained no additive specified by our invention. The dielectric bodies formulated accordingly were not coherently bonded on firing at a temperature as high as 1300* C. Consider the ceramic compositions of Tests Nos. 40, 47 and 52 for comparison. They contained 0.2 part by weight of the additives with respect to 100 parts by weight of the major ingredient. Even though the firing temperature was as low as 1160-1180. C., the resulting test capacitors possess the desired electrical characteristics. We set, therefore, the lower limit of the possible proportions of the additive mixture at 0.2 part by weight with respect to 100 parts by weight of the major ingredient.
- The Tests Nos. 45, 50 and 55 ceramic compositions contained as much as 12 parts by weight of the additives with respect to 100 parts by weight of the major ingredient. The resulting Tests Nos. 45, 50 and 55 capacitors have average Q factors of 1050, 1050 and 1130, respectively, which are all far less than the above established criterion of 3200. When the proportion of the additive mixture was reduced to 10 parts by weight, as in Tests Nos. 44, 49 and 54, the resulting capacitors have all the desired characteristics. Therefore, the upper limit of the possible proportions of the additive mixture is set at 10 parts by weight with respect to 100 parts by weight of the major ingredient.
- As for the major ingredient, (CaO) k·(Zr1-xTix)O2, the value of x was set at 0.35 and more in Tests Nos. 37 and 38. In the resulting capacitors the temperature coefficient of capacitance is -840 and -980, both outside the desired range of -690 to +30. When the value of x was decreased to not more than 0.30, as in Test No. 36, then the desired electrical charactristics were all obtained. The highest possible value of x is therefore 0.30. Test No. 28 indicates that the desired electrical characteristics are obtainable if the value of x is zero, that is, if the major ingredient does not include titanium. The Q factor becomes-relatively high if the value of x is reduced to less than 0.20.
- The value of k in the formula of the major ingredient was set at 0.7 in Tests Nos. 56 and 62. The resistivities of the resulting capacitors were 5.4 x 10 and 3.6 x 103, both much lower than the desired lower limit of 1 x 107. The desired value of resistivity was obtained when the value of k was increased to 0.8 as in Test No. 57 and 63. The lowermost possible value of k is therefore 0.8. On the other hand, when the value of k was made as much as 1.4 as in Tests Nos. 61 and 67, the resulting dielectric bodies were not coherently bonded on firing at as high a temperature as 1300° C. The desired electrical characteristics were obtained when the value of k was reduced to 1.3 as in Tests Nos. 60 and 66. Accordingly, the greatest possible value of k is 1.3.
- We have ascertained from the results of Table 2 that the acceptable range of the relative proportions of B2O3, SiO2 and MO, the additives of the ceramic compositions in accordance with our invention, can be definitely stated in reference to the ternary diagram of FIG. 2.
- The point A in the ternary diagram indicates the Test No. 1 additive composition of 15 mole percent B2O3, 25 mole percent SiO 2 and 60 mole percent MO. The point B indicates the Test No. 2 additive composition of 30 mole percent B 0 , zero mole percent Si0 and 70 mole percent MO. The point C indicates the Test No. 3 additive composi- tion of 90 mole percent B 0 , zero mole percent SiO2 and 10 mole percent MO. The point D indicates the Test No. 4 additive composition of 90 mole percent B2O3, 10 mole percent SiO2 and zero mole percent MO. The point E indicates the Test No. 5 additive composition of 25 mole percent B 0 , 75 mole percent SiO2 and zero mole percent MO.
- The relative proportions of the additives B 0 , SiO2 and MO of the ceramic compositions in accordance with our invention are within the region bounded by the lines sequentially connecting the above stated points A, B, C, D and E in the ternary diagram of FIG. 2.
- Tables 1 and 2 prove that the additive compositions within the above defined region makes possible the provision of capacitors of the desired electrical characteristics. The additive compositions of Tests Nos. 23-27 all fall outside that region, and the corresponding dielectric bodies were not coherently bonded on firing at a temperature of 1250* C. The above specified acceptable range of the relative proportions of the additives holds true regardless of whether only one of BaO, MgO, ZnO, Sr0 and CaO is employed as MO, as in Tests Nos. 9-13, or two or more or all of them are employed in suitable relative proportions as in other Tests.
- Although we have disclosed our invention in terms of specific Examples thereof, we understand that our invention is not to be limited by the exact details of such disclosure but admits of a variety of modifications or alterations within the usual knowledge of the ceramists, chemists or electricians without departing from the scope of the invention. The following, then, is a brief list of such possible modifications or alterations:
- 1. The low temperature sinterable ceramic compositions of our invention may include various additives not disclosed herein. An example is a mineralizer such as manganese dioxide. Used in a proportion (preferably from 0.05 to 0.10 percent by weight) not adversely affecting the desired characteristics of the resulting capacitors, such a mineralizer will lead to the improvement of sinterability.
- 2. The start materials of the ceramic compositions in accordance with our invention may be substances such as oxides or hydroxides other than those employed in the foregoing Examples.
- 3.' The temperature of the oxidizing heat treatment need not necessarily be 600* C. but can be variously determined in a range (from 500° to 1000' C. for the best results) not exceeding the temperature of the preceding sintering in a nonoxidative atmosphere, the oxidizing temperature being dependent upon factors such as the particular base metal electrode material in use and the degree of oxidation required for the ceramic material.
- 4. The temperature of cosintering in a nonoxidative atmosphere may also be changed in consideration of the particular electrode material in use. We recommend a range of 1050° to 1200° C. if the electrode material is nickel, as we have ascertained from experiment that little or no flocculation of the nickel particles takes place in that temperature range.
- 5. The dielectric bodies and electrodes may be cosintered in a neutral, instead of reductive, atmosphere.
- 6. The ceramic compositions disclosed herein may be employed for capacitors other than those of the multilayered configuration.
Claims (9)
Applications Claiming Priority (2)
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JP60270543A JPS62131414A (en) | 1985-11-30 | 1985-11-30 | Dielectric porcelain compound |
JP270543/85 | 1985-11-30 |
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EP0226071A2 true EP0226071A2 (en) | 1987-06-24 |
EP0226071A3 EP0226071A3 (en) | 1989-05-24 |
EP0226071B1 EP0226071B1 (en) | 1991-08-14 |
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US (1) | US4709299A (en) |
EP (1) | EP0226071B1 (en) |
JP (1) | JPS62131414A (en) |
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Cited By (1)
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EP0228669A2 (en) * | 1985-12-30 | 1987-07-15 | Taiyo Yuden Co., Ltd. | Low temperature sintered ceramic capacitor with a temperature compensating capability, and method of manufacture |
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JPS63281309A (en) * | 1987-05-12 | 1988-11-17 | Taiyo Yuden Co Ltd | Porcelain capacitor |
EP0376670B1 (en) * | 1988-12-27 | 1995-08-09 | Kabushiki Kaisha Toshiba | A high-dielectric constant ceramic composite and ceramic capacitor elements |
US20130127174A1 (en) * | 2013-01-15 | 2013-05-23 | Duncan G. Cumming | Method for Generating Tidal Energy Utilizing the Scalar Gravitational Potential of Celestial Bodies |
Citations (2)
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EP0187960A2 (en) * | 1984-12-18 | 1986-07-23 | Taiyo Yuden Co., Ltd. | Low temperature sintered ceramic capacitor with high DC breakdown voltage, and method of manufacture |
EP0187959A1 (en) * | 1984-12-18 | 1986-07-23 | Taiyo Yuden Co., Ltd. | Low temperature sintered ceramic capacitor with high DC breakdown voltage, and method of manufacture |
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JPS5398099A (en) * | 1977-02-07 | 1978-08-26 | Murata Manufacturing Co | Nonnreducction type dielectric ceramic composition for temperature compensation |
US4223369A (en) * | 1978-07-03 | 1980-09-16 | Sprague Electric Company | Monolithic capacitor with low firing zirconate and nickel electrodes |
DE3270911D1 (en) * | 1981-12-21 | 1986-06-05 | Matsushita Electric Ind Co Ltd | High dielectric constant porcelain composition |
JPS5920908A (en) * | 1982-07-26 | 1984-02-02 | 株式会社村田製作所 | Temperature compensating dielectric porcelain composition |
JPS60115105A (en) * | 1983-11-24 | 1985-06-21 | ティーディーケイ株式会社 | Dielectric porcelain composition |
EP0155364B1 (en) * | 1983-11-30 | 1989-03-08 | Taiyo Yuden Co., Ltd. | Low temperature sintered ceramic materials for use in soliddielectric capacitors or the like, and method of manufacture |
EP0155365B1 (en) * | 1983-11-30 | 1989-02-08 | Taiyo Yuden Co., Ltd. | Low temperature sintered ceramic materials for use in solid dielectric capacitors or the like, and method of manufacture |
JPS60118667A (en) * | 1983-11-30 | 1985-06-26 | 太陽誘電株式会社 | Dielectric ceramic composition |
-
1985
- 1985-11-30 JP JP60270543A patent/JPS62131414A/en active Granted
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1986
- 1986-11-20 EP EP86116195A patent/EP0226071B1/en not_active Expired - Lifetime
- 1986-11-20 DE DE8686116195T patent/DE3680883D1/en not_active Expired - Fee Related
- 1986-11-25 US US06/934,667 patent/US4709299A/en not_active Expired - Lifetime
- 1986-11-28 KR KR1019860010081A patent/KR900008778B1/en not_active IP Right Cessation
Patent Citations (2)
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EP0187960A2 (en) * | 1984-12-18 | 1986-07-23 | Taiyo Yuden Co., Ltd. | Low temperature sintered ceramic capacitor with high DC breakdown voltage, and method of manufacture |
EP0187959A1 (en) * | 1984-12-18 | 1986-07-23 | Taiyo Yuden Co., Ltd. | Low temperature sintered ceramic capacitor with high DC breakdown voltage, and method of manufacture |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
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EP0228669A2 (en) * | 1985-12-30 | 1987-07-15 | Taiyo Yuden Co., Ltd. | Low temperature sintered ceramic capacitor with a temperature compensating capability, and method of manufacture |
EP0228669A3 (en) * | 1985-12-30 | 1989-05-31 | Taiyo Yuden Co., Ltd. | Low temperature sintered ceramic capacitor with a temperature compensating capability, and method of manufacture |
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EP0226071B1 (en) | 1991-08-14 |
JPH0552603B2 (en) | 1993-08-05 |
KR900008778B1 (en) | 1990-11-29 |
EP0226071A3 (en) | 1989-05-24 |
KR870005421A (en) | 1987-06-08 |
JPS62131414A (en) | 1987-06-13 |
DE3680883D1 (en) | 1991-09-19 |
US4709299A (en) | 1987-11-24 |
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